South Caifornia

Diver Matt Pressly broke the water’s surface with a cloud of bubbles and clipped a bag containing a single sea urchin to an orange buoy bobbing beside him in the water off San Diego. For more than 30 years, Pressly has been diving off the coast of California for sea urchins, sold in sushi restaurants as a delicacy called “uni.” Divers collect both red and purple varieties. In that time, he’s seen urchins move to deeper water in search of the kelp they feed off ‒ kelp that in some cases no longer grows the way it used to. Scientists say hotter water is rapidly changing the ecosystems of California coastal areas. Among the changes: less kelp in shallower areas. “It used to be that you’d be in deep, deep kelp by now,” Pressly said after catching his breath. “But it’s been gone for five years and hasn’t come back. So I’m having to go out deeper to find the kelp.” For 30 minutes, P...